This capacitive sensor that operates with a high frequency oscillator was found in Radio Electronics from the 90's. The circuit operates around 300 kHz.
This circuit from the 70's used germanium transistors and operated in the range of medium and...
The figure shows how to convert a rectangular signal into a triangular signal using an integrator. The...
This circuit was found in a National Semiconductor manual from the 1970s, appearing in articles and on...